Apparatus and method of block acknowledgements with reduced recipient state information

ABSTRACT

An apparatus and method for block acknowledgements with reduced recipient state information are described. In one embodiment, the method comprises the storing of a receive state for a block of frames received during a transmission opportunity (TXOP) with an on-chip state memory. Once stored, an immediate block acknowledgement, including the receive state information, may be transmitted to an originator according to a block acknowledgement request (BAR) received during the TXOP. In the embodiments described, the BAR is received during the TXOP in which the block of data frames were transmitted to a recipient. In one embodiment, the recipient is free to discard the receive state information to free space within the on-chip system memory by requiring the originator to maintain the receive state information of blocks of data frames transmitted during TXOPs. Other embodiments are described and claimed.

FIELD

One or more embodiments relate generally to the field of wirelesscommunications. More particularly, one or more of the embodiments relateto a method and apparatus of block acknowledgements with reducedrecipient state information.

BACKGROUND

Any Wireless Local Area Network (WLAN) device that supports an Instituteof Electrical and Electronics Engineers (IEEE) 802.11 Standard (e.g.,IEEE Std. 802.11-1997, 802.11a, 802.11e, etc.) includes two mainparts: 1) a physical (PHY) layer signaling control device; and 2) amedium access control (MAC) device. The function of the PHY device is totransfer data packets over the air interface. Among other things, thefunction of the MAC device is to fairly control access to the shared airinterface.

The minimal MAC protocol consists of two frames: 1) a frame sent from atransmitter to a receiver; and 2) an acknowledgement (ACK) from thereceiver that the frame was received correctly. If a transmitter hasmultiple packets to send to the receiver, some versions of the 802.11Standard require the transmitter to wait for an ACK after transmissionof each packet. In addition, the transmitter must wait for a particulartime interval, referred to as the Interframe Space (IFS), afterreceiving the ACK and before transmitting the next packet.

Other versions of the 802.11 Standard (e.g., IEEE Std. 802.11e) supporttransmission of packets with selective acknowledgement. This feature isreferred to as “Block ACK.” The Block ACK feature enables thetransmitter to send the next packet to the same receiver withoutnecessarily waiting for an ACK. Instead, after negotiating for access tothe air interface, the transmitter sends the first packet, waits aninter-frame space (IFS) after the end of the first packet, and sends thenext packet. After the transmitter has sent all of its packets to thereceiver, the transmitter asks the receiver for a response, whichindicates an ACK for all of the previously transmitted packets.

The Block ACK (BA) mechanism provided by the 802.11e Standard isreferred to herein as the “immediate BA mechanism.” The immediate BAmechanism provided by the 802.11e Standard is essential for realizingthe throughput gains expected with 802.11n. However, the existingprotocol imposes large memory requirements on devices that support thisoptional feature. The immediate BA protocol allows an originator to senda block data frames to a recipient and then request an acknowledgementfor the block. To do this, the recipient maintains a scoreboard with astarting sequence number (SSN) and a bit marking each received dataframe per each of established BA agreements. The process is under thecontrol of the originator, which decides when the data frames are sentand when the block acknowledgement request (BAR) is sent to solicit aBA.

BRIEF DESCRIPTION OF THE DRAWINGS

The various embodiments of the present invention are illustrated by wayof example, and not by way of limitation, in the figures of theaccompanying drawings and in which:

FIG. 1 is a block diagram illustrating a peer-to-peer wireless networkconfiguration for providing block acknowledgements with reducedrecipient state information, in accordance with one embodiment.

FIG. 2 is a block diagram illustrating a wireless network (WLAN)configuration for providing block acknowledgements with reducedrecipient state information, in accordance with one embodiment.

FIG. 3 is a block diagram illustrating an immediate blockacknowledgement (ACK) (BA) with reduced recipient state information, inaccordance with one embodiment.

FIG. 4 is a block diagram illustrating a wireless configuration toprovide block ACK with a reduced recipient state information, inaccordance with one embodiment.

FIG. 5 is a block diagram further illustrating block ACK logic of FIG.4, in accordance with one embodiment.

FIG. 6 is a block diagram further illustrating the communicationsinterface of FIGS. 4 and 5, in accordance with one embodiment.

FIG. 7 is a state flow diagram illustrating a block ACK request andblock ACKs with reduced recipient state information, in accordance withone embodiment.

FIG. 8 is flowchart illustrating a method for restricting the behaviorof an originator to provide block ACKs with reduced recipient stateinformation, in accordance with one embodiment.

FIG. 9 is a flowchart illustrating a method for responding to a blockACK request with a reduced recipient state information, in accordancewith one embodiment.

DETAILED DESCRIPTION

A method and apparatus for block acknowledgements (ACK) (BA) withreduced recipient state information are described. In one embodiment,the method comprises the storing of a receive state for a block offrames received during a transmission opportunity (TXOP) with an on-chipstate memory. Once stored, an immediate block ACK (BA), including thereceive state information, may be transmitted to an originator accordingto a BA request (BAR) received during the TXOP. In one embodiment, theoriginator is required to issue the BAR during the TXOP in which theblock of data frames were transmitted to a recipient. In one embodiment,the recipient is free to discard the receive state information to freespace within the on-chip system memory by requiring the originator tomaintain the receive state information of blocks of data framestransmitted during TXOPs.

System

FIG. 1 is a block diagram illustrating a peer-to-peer (ad-hoc)configuration for a wireless network 100, in accordance with oneembodiment of the invention. FIG. 2 illustrates an infrastructure modeor basic service set (BSS) wireless local area network (WLAN)configuration 150, in accordance with one embodiment. In embodimentsdepicted in FIGS. 1 and 2, wireless networks 100 and 150 may beconfigured according to a “wireless protocol” including, but not limitedto, IEEE 802.11a, 802.11b, 802.11c, 802.11e, 802.11g, 802.11n, 802.11i,HyperLan 2, or any other protocol for any point-to-point (ad-hoc)wireless link or network. In one embodiment, wireless clients 102, asshown in FIGS. 1 and 2, are configured to provide a blockacknowledgement (ACK) (BA) with reduced recipient state information toreduce storage requirements of a recipient station, according to oneembodiment.

As shown in FIG. 1, network 100 is configured according to an ad hocmode as independent basic service set (IBSS). Representatively, two ormore wireless clients 102 (102-1, . . . , 102-N) are equipped with, forexample, wireless adapter cards to communicate within wireless network100. As illustrated in FIG. 2, in the infrastructure mode, each client102 sends all communications to a WLAN access point (station) 160. Assuch, the clients 102 communicate with station 160, which acts as abridge to resources of a wired network 170. Wired network 170 mayimplement a local area network (LAN) using an Ethernet protocol, HomePlug protocol, or the like.

As described herein, the term “wireless client” or “client” is used torefer to wireless devices including, but not limited to, personalcomputers including laptop computers, equipped with wireless adaptercards, as well as personal digital assistants (PDAs), appliances, andthe like devices configured to communicate via a wireless communicationsmedium such as, for example, radio frequency (RF) waves. Furthermore, asdescribed herein, the term “wireless station” or “station” is used torefer to devices including, but not limited to, wireless base stations,wireless access points (AP), computers such as server computers,personal computers, laptops, PDAs, or like devices configured torestrict access to stored information contained therein or to anattached wired network.

FIG. 3 illustrates a block acknowledgement (BA) sequence according to animmediate BA mechanism with a reduced recipient state information, inaccordance with one embodiment. However, there are two types of BAmechanisms: immediate and delayed. Immediate BAs are suitable forhigh-bandwidth, low latency traffic, while delayed BAs are suitable forapplications that tolerate moderate latency. As described herein, thestation with data to send using the BA mechanism, is referred to as the“originator” and the receiver of that data as the “recipient.”

In one embodiment, the immediate BA mechanism illustrated in FIG. 3 mayimprove channel efficiency by aggregating several acknowledgements (ACK)into one frame. The immediate BA mechanism, as shown in FIG. 3, isessential for realizing the throughput gains expected with IEEE 802.11nStandard. However, the immediate BA mechanism as it is defined in IEEE802.11e imposes large memory requirements on recipients that supportthis feature. As shown in FIG. 3, the immediate BA mechanism allows theoriginator 182 to send a block 186 of data frames 188 (188-1, 188-2,188-3, 188-4), such as, for example, quality of service (QoS) data torecipient 184 and then perform BA-BAR exchange 190 to receive a BA 194for the block 186.

As described herein, a “BA-BAR exchange” may refer to the issuance of aBA request (BAR) (e.g., BlockAckReq 192) by an originator (e.g.,originator 182) and issuance of a BA (e.g., BlockAck 194) that areperformed within a current transmit opportunity (TXOP) (e.g., asindicated by TXOP Start 196 and TXOP End 198). In one embodiment, BAR-BAexchange 190 is performed within the current TXOP to reduce recipientstorage of receive state information for received data frames byenabling the recipient to discard the receive state informationsubsequent to termination of the TXOP. As indicated by item 199, storagerequirements of the recipient 184, for maintaining receive stateinformation of issued data frames to enable the immediate BA mechanism,are reduced by limiting a recipient to having, at most, one BA bitmap(for storage of the receive state information) per transmit identifier(TID). Although illustrated in FIG. 3 as media access control (MAC)protocol data units (MPDUs) of QoS data, the embodiments describedherein are not limited to MPDU QoS data and may be used for other likeframe formats or packet formats, such as non-QoS MPDUs or other likepacket format.

As shown in FIG. 3, the BA exchange 190 is performed by issuing a BArequest (BAR) 192 prior to termination of the current TXOP (TXOP END)198. In response, the recipient issues BA 194 to complete the BAR-BAexchange 190. To provide an acknowledgement for the entire block of dataframes requires recipient 182 to maintain some sort of stateinformation, such as, for example, a BA bitmap with a starting sequencenumber (SSN) and bit marking each received data frame. As shown in FIG.3, the process is under the control of originator 182, which decideswhen data frames are sent and when the BAR-BA exchange 190 is performedto receive an immediate BA 194 from recipient 184.

Supporting the immediate BA mechanism requires that recipient 184maintain a BA bitmap per BA agreement. As described herein, a “BAagreement” may refer to an agreement between an originator and arecipient to require the recipient to issue an immediate BA in responseto a BAR issued by the originator. The storage requirements in a deviceare determined by the maximum number of active BA sessions. Up to 16(maximum number of traffic identifier (TID)) sessions may be activebetween any two stations. The maximum number of peer stations is almostunlimited, although in practice, some limit is chosen based on theexpected usage. The storage requirements are thus:

#BITMAP=(#TA*#TID)  (1)

Accordingly, since a recipient must respond immediately to a BAR 192with a BA 194 to complete BAR-BA exchange 190, these bitmaps must bestored in low latency, on-chip memory. Accordingly, in one embodiment,as shown in FIG. 3, the behavior of originator 182 is restricted torequire originator to issue the BAR 192 prior to termination of atransmit opportunity (TXOP END) 198. Accordingly, as shown in FIG. 3,originator 182 is constrained to limit the information that is returnedin an immediate BA 194. By restricting the behavior of originator 182,recipient 184 is allowed to reduce low latency, on-chip memoryrequirements, while maintaining a single scoreboard or BA bitmap (or afixed number of scoreboards) and re-use the BA bitmap for different BAsessions. In one embodiment, the storage requirements may be reduced to:

BitMap(per TID bitmap)=#TID  (2)

FIG. 4 is a block diagram illustrating originator station 200 to supportan immediate BA mechanism with reduced recipient state, in accordancewith one embodiment. Representatively, station 200 may include amicroprocessor 202, which uses chipset 210 to access on-chip statememory 250, as well as communications interface 220. In one embodiment,memory 250 includes, but is not limited to random access memory (RAM),dynamic RAM (DRAM), static RAM (SRAM), synchronous DRAM (SDRAM), doubledata rate (DDR) SDRAM (DDR-SDRAM), Rambus DRAM (RDRAM) or any devicecapable of supporting high-speed buffering of data. As described herein,the term “chipset” is used in a manner well know to those of ordinaryskill in the art to describe, collectively, the various devices coupledto CPU 202 to perform desired system functionality.

In one embodiment, communications interface 220 is, for example, awireless Physical Layer, which operates according to a multipleinput/multiple output (MIMO) operation. In accordance with such anembodiment, station 200 includes multiple transmit and receive antennas230 (230-1, . . . , 230-N). Representatively, station 200 providesmultiple TX antennas and in one embodiment, includes blockacknowledgement request BAR 300 for support an immediate BA mechanismwith reduced recipient state level. In one embodiment, MAC layerfunctionality is provided by chipset 210 and BAR logic 300 and PHY layerfunctionality is provided by communication interface 220.

Accordingly, in the embodiment illustrated in FIG. 4, blockacknowledgement request (BAR) logic 300 restricts originator behavior asshown in FIG. 3. As illustrated, BAR logic 300, following establishingof a BA session (entering into BA agreement using BA agreement logic340) between a recipient and an originator, monitors the originator'stransmission of a burst of frames to a recipient address (RA) for asingle traffic identifier (TID). In accordance with such an embodiment,BAR logic 300 restricts the originator to require the originator totransmit a block acknowledgement request (BAR) before the end of thecurrent transmit opportunity (TXOP).

In one embodiment, BAR-BA exchange logic 310 requires originator station200 to initiate a BAR-BA exchange within a current TXOP. As shown inFIG. 3, transmission of a block of data frames 186 may begin within apolled TXOP or by contended channel access, such as, for example, anenhanced distributed channel access (EDCA) contention (TXOP Start 196).As shown in FIG. 3, a TXOP Start 196 is detected by originator 182. Oncedetected, a BA session begins with the originator issuing MPDU datablock 186 of QoS data frames 188.

Referring again to FIG. 4, BAR-BA exchange logic 340 monitors the TXOPto ensure that originator station 200 issues the BAR prior totermination of the TXOP. Once the BAR is issued to the recipient,receive state logic 320 determines a received state of each of theframes transmitted to the recipient, according to, for example, a BAcontrol frame received from the recipient, including, for example, a BAbitmap. In response to the received BA, a state of transmit queue 330may be updated to retransmit unacknowledged frames. However, foracknowledged frames, discard logic 350 may discard acknowledged frames.

As shown in FIG. 4, station 200 is shown as operating as an originatorstation within a BA session. In the embodiment illustrated, BAR logic300 is shown separate from chipset 210. However, in the embodimentsdescribed, BAR logic 300 may be integrated within chipset 210 orimplemented as firmware within station 200, while remaining within thescope of the embodiments, as defined by the appended claims. Likewise,BA logic 400, although shown as integrated within chipset 210, may beprovided as a separate off-chip component, for example, as illustratedin FIG. 5, may be provided as firmware within station 220, whileremaining within the scope of the embodiments described herein, asdefined by the appended claims Representatively, as shown, chipset 210may include BA logic 400 for situations where station 200 operates as arecipient station, for example, as shown in FIG. 5.

FIG. 5 is a block diagram of station 200, as shown in FIG. 4, to furtherillustrate BA logic 400 with BAR logic 300, as shown in FIG. 4,implemented within chipset 210, according to one embodiment.Representatively, BA agreement logic 430, establishes a BA agreementwith an originator. Once established, BA bitmap logic 420 may maintainreceive state information for received data frames within BA bitmap 402for a single transmitter address (TA) and traffic identifier (TID) atany one time. Upon receipt of a data frame, BA bitmap logic 420 checks aTA and TID of the received data frame against BA bitmap 402. If a matchis detected, BA bitmap logic 420 marks BA bitmap 402 for the receiveddata frame.

In one embodiment, reset logic 450 may reset BA bitmap 402 and reuse BAbitmap 402 if a match is not detected between the TA and TID of thereceived data frame and the TA and TID of BA bitmap 402. Upon receipt ofa BAR issued by an originator, BAR-BA logic 410 may compare a TA and TIDof the received BAR against BA bitmap 402. If a match is detected,BAR-BA exchange logic 460 may request BA control frame logic 440 toissue a BA control frame to the originator, including BA bitmap 402.

In one embodiment, BA control frame logic 440 includes shift logic (notshown) to shift BA bitmap 402 according to a starting sequence number(SSN) detected from the BAR received from the originator. Otherwise, BAcontrol frame logic 440 may respond with a null BA, which is, forexample, a BA including all zero values. Upon receipt of the BAR, in oneembodiment, frame release logic 410 may determine whether a continuoussequence of data frames started from the SSN are available within, forexample, reorder buffer 470. When such is the case, frame release logic460 may release the continuous sequence of received data frames fromreorder buffer 470.

FIG. 6 is a simplified block diagram further illustrating communicationsinterface 220 (e.g., stations, as shown in FIGS. 4 and 5) in accordancewith one embodiment. Any WLAN station 200 may provide support for IEEE802.11 Standard by including a physical layer (PHY) signaling controldevice (PHY device) 240, a medium access control (MAC) device 224, and aMAC client 222. In one embodiment, the function of MAC device 224 may bemodified to operate according to BAR logic 300 (FIG. 4) and BA logic 400(FIG. 5) to support the immediate BA mechanism with a reduced recipientstate.

The MAC client 222 creates and processes data, among other things. Thepurpose of the PHY and MAC devices 240, 224 is to ensure that twonetwork stations are communicating with the correct frame format andprotocol. An IEEE Std. 802.11 defines the communication protocol betweennetwork stations.

The function of the PHY device 240 is threefold: 1) to provide a frameexchange between the MAC 224 and PHY 240 under the control of a physicallayer convergence procedure (PLCP) sublayer; 2) to transmit data framesover the air interface under the control of the physical mediumdependent (PMD) sublayer; and 3) to provide a carrier sense indicationback to the MAC 224 so the MAC 224 is able to verify activity on the airinterface. In one embodiment, PHY device is modified to provide acombined rate and TX antenna selection mechanism.

In general, the PHY device 240 includes PLCP apparatus 242, and transmitand receive PMD apparatuses 242, 244. Each of these may or may not usesome or all of the same physical circuitry (e.g., processors, busses,clocks, storage, etc.). In addition, a plurality of antennas 230 (230-1,. . . , 230-N) may be interconnected with PMD apparatus 242, 244.

FIG. 7 is a block diagram illustrating a reduced recipient state flow500, in accordance with one embodiment. As illustrated, originator 510and recipient 550 have entered into a BA agreement and during a BAsession, originator 510 issues a sequence MAC protocol data unit (MPDU)blocks of QoS data frames 520, 522 and 524 during TXOP 502 to RAI andTIDI. Once issued and prior to termination of TXOP 502, originator 502issues BAR 512 to recipient 550. As illustrated, data frames 522 and 524are received by recipient 550 but data frame 520 is not received.Accordingly, the recipient's BA bitmap 552 illustrates receipt of dataframes 522 and 524.

Representatively, recipient 550 only receives frames 522 and 524;therefore in BA bitmap 552, the first up to date bit is related to frame522. In the time the recipient 550 receives BAR 512-1, the bits relatedto frames 522 and 524 are set in BA bitmap 552. Upon receipt of BAR512-1 with SSN=1, recipient 550 checks BA bitmap 552 and recognizes thatframe 520 does not succeed and answers with the related BA control frame554-1 that acknowledges frames 522 and 524. In parallel, recipient 550checks the reordering buffer 556 and sees that there is no sequence thatcan be released. Upon receipt of BA control frame 554-1, the originatorupdates its own bitmap 514 related to the particular RA1/TID1 withsuccess of frame 522 and frame 524 and remembers that the frame 520should be retransmitted.

In next transmit opportunity 504, originator 510 starts to send dataframes 530, 532 and 534 to RA1 and TID 2. Recipient 550 receives onlyframe 534, as shown, frames 530 and 532 are not received. At this point,recipient 550 recognizes that the TID (TID2) differs from the former(TID1) and therefore resets the memory allocated for bitmap 552 andstarts the new bitmap 552 related to new TID2 in the same location. TheBAR-BA exchange behavior of originator 510 and recipient 550 may be thesame as described for TID1. In one embodiment, originator 510 hasseparate resources for bitmap 514, as well as for actual data frames perRA/TID; recipient 550 has separate reordering buffers 556 for dataframes per TA/TID, but may include only single shared resource forbitmap 552.

In the next transmit opportunity 506, the originator 510 resumestransmission to the TID1. Representatively, the frames (526, 528, 520)are issued out of order with frames 526 and 528 issued prior toretransmission of frame 520. At the first received frame 526, therecipient 550 recognizes that the TID differs from the last one, resetsthe memory and starts to build bitmap 552 related to TID1. The recipient550 successfully receives all sent frames 526, 528 and 520.

Representatively bitmap 552 reflects the success of frames 520, 526 and528 with numbers 1, 4 and 5, respectively. This bitmap 552 does notcontain the former success of frames 522 and 524. The BAR 512-3 issuedby the originator 510 repeats the former SSN=1 and the recipient 550responds with BA 554-3 that acknowledges the frames 520, 526 and 528.The bitmap 552 contained in BA control frame 554-3 actually is anincrement of the last sent bitmap 552. After getting this BA 552, theresulting bitmap 514 stored by the originator 510 will containcontinuous sequences of frames from 1 until 5, thus allowing shiftingthe SSN to 6.

At getting BAR 512-3, the recipient 550 goes to check its reorderingbuffer 556 per related TA/TID. It now contains a continuous sequence offrames from 1 until 5, thus enabling releasing of frames 520-528 toupper layers and freeing the related buffers. The originator 510 alsoreleases the related frames and buffers. Representatively, FIG. 7 maydemonstrate how the method for immediate BA mechanism with reducedrecipient state information succeeds to deliver MPDU frames 520-528;however, the related bitmap 552 is reset in the middle of the BA sessionand used by another flow. Procedural methods for implementing one ormore embodiments are now described.

Operation

Turning now to FIG. 8, the particular methods associated withembodiments of the invention are described in terms of computer softwareand hardware with reference to a flowchart. The methods to be performedby a computing device (e.g., a wireless station) may constitute statemachines or computer programs made up of computer-executableinstructions. The computer-executable instructions may be written in acomputer program and programming language or embodied in firmware logic.If written in a programming language conforming to a recognizedstandard, such instructions can be executed in a variety of hardwareplatforms and for interface to a variety of operating systems.

In addition, embodiments of the invention are not described withreference to any particular programming language. It will be appreciatedthat a variety of programming languages may be used to implementembodiments of the invention as described herein. Furthermore, it iscommon in the art to speak of software, in one form or another (e.g.,program, procedure, process, application, etc.), as taking an action orcausing a result. Such expressions are merely a shorthand way of sayingthat execution of the software by a computing device causes the deviceto perform an action or produce a result.

FIG. 8 is a flowchart illustrating a method 600 for blockacknowledgements with reduced recipient state information, in accordancewith one embodiment. In the embodiments described, examples of thedescribed embodiments will be made with reference to FIGS. 1-7. However,the described embodiments should not be limited to the examples providedto limit the scope of the various embodiments, as defined by theappended claims.

Referring again to FIG. 8, at process block 610, an originator mayrequest a BA agreement with a recipient. Once requested, it isdetermined, at process block 620, whether the BA agreement is accepted.Once accepted, the originator may engage in a BA session by detecting aTXOP at process block 630. Once detected, the originator may transmit ablock of data frames to the recipient. Once transmitted, at processblock 650, the originator issues a BAR to the recipient to request animmediate BA. Once requested, at process block 660, it is determinedwhether the originator has received a BA control frame. Once received,at process block 670, the originator may update a transmit (TX) queuestate according to a BA bitmap received with the control frame. Based onthe BA bitmap, the originator may retransmit unacknowledged frames anddiscard acknowledged frames.

Corresponding behavior of a recipient is shown in the flowchart of FIG.9 to illustrate a method 710 for an immediate BA mechanisms with areduced recipient state, in accordance with one embodiment. At processblock 710, the recipient determines whether a block agreement request isreceived. Once received, at process block 720, the recipient may acceptthe BA agreement. Once accepted, at process block 730, the recipient mayissue acceptance of a BA agreement to the originator.

In one embodiment, the establishment of a BA agreement, as illustratedby process blocks 710-730 and corresponding process blocks 610 and 620of FIG. 8, may be performed by exchanging an add BA (ADDBA) request andresponse frames. Specifically, the originator issues an ADDBA request tothe recipient, which is acknowledged by the recipient. Subsequent tosuch acknowledgement, the recipient may send an ADDBA response frame tothe originator, which may either accept or reject the BA agreement.Receipt of such ADDBA response frame is acknowledged by the originatorto the recipient to establish a BA agreement.

Referring again to FIG. 9, at process block 740, a BA agreement has beenestablished and now the recipient determines whether a block of framesis received. As the block of frames is received, at process block 750,the recipient may update a BA bitmap for received data frames. Onceupdated, at process block 760, it is determined whether a BAR s receivedfrom the originator. Once received, at process block 770, the recipientdetermines whether the BAR was received during the current TXOP. Ifreceived during the current TXOP, at process block 780, the recipientmay issue the BA bitmap to the originator within a BA control frame.Once transmitted, at process block 790, the recipient is able to reducerecipient state information by resetting the BA bitmap, once the BAcontrol frame is acknowledged by the originator. Accordingly, since theoriginator is responsible for maintaining the receive state informationonce the originator has received the BA control frame, including areceive state of each of the data frames issued to the recipient duringthe current TXOP, the recipient is no longer responsible for suchinformation.

Accordingly, in the embodiments illustrated, for example, as shown inFIGS. 4 and 5, one embodiment of the immediate BA mechanism, asdescribed herein, may provide a reduced recipient state by using asingle resource for the recipient BA bitmap, irrespective of the numberof active BA sessions the recipient maintains. As the result of the useof a single resource for the recipient bitmap, significantly fewermemory resources may be required within local memory, as compared to theunconstrained immediate BA mechanism, for example, as described by802-11e. Due to the reduced local memory requirements, wireless devices,which implement the immediate BA mechanism, as described herein, may bemanufactured with a significantly reduced product cost.

Accordingly, in the embodiments described with reference to FIGS. 4 and5, recipient station 200 contains a single resource for storing andmaintaining a BA bitmap that is used for any BA agreements of therecipient station. In one embodiment, the BA bitmap may be reset inresponse to recipient station detection of a change of TA/TID accordingto a received data frame. To support the immediate BA mechanism with areduced recipient state, the originator may maintain a BA bitmap in anincremental manner storing untouched fields related to formerlyacknowledged MPDUs and updating only fields relating to new acknowledgedMDPUs regarding the particular RA/TID combination.

Elements of embodiments of the present invention may also be provided asa machine-readable medium for storing the machine-executableinstructions. The machine-readable medium may include, but is notlimited to, flash memory, optical disks, compact disks-read only memory(CD-ROM), digital versatile/video disks (DVD) ROM, random access memory(RAM), erasable programmable read-only memory (EPROM), electricallyerasable programmable read-only memory (EEPROM), magnetic or opticalcards, propagation media or other type of machine-readable mediasuitable for storing electronic instructions. For example, embodimentsof the invention may be downloaded as a computer program which may betransferred from a remote computer (e.g., a server) to a requestingcomputer (e.g., a client) by way of data signals embodied in a carrierwave or other propagation medium via a communication link (e.g., a modemor network connection).

It should be appreciated that reference throughout this specification to“one embodiment” or “an embodiment” means that a particular feature,structure or characteristic described in connection with the embodimentis included in at least one embodiment of the present invention.Therefore, it is emphasized and should be appreciated that two or morereferences to “an embodiment” or “one embodiment” or “an alternativeembodiment” in various portions of this specification are notnecessarily all referring to the same embodiment. Furthermore, theparticular features, structures or characteristics may be combined assuitable in one or more embodiments of the invention.

Similarly, it should be appreciated that in the foregoing description ofembodiments of the invention, various features are sometimes groupedtogether in a single embodiment, figure, or description thereof for thepurpose of streamlining the disclosure aiding in the understanding ofone or more of the various inventive aspects. This method of disclosure,however, is not to be interpreted as reflecting an intention that theclaimed subject matter requires more features than are expressly recitedin each claim. Rather, as the following claims reflect, inventiveaspects lie in less than all features of a single foregoing disclosedembodiment. Thus, the claims following the detailed description arehereby expressly incorporated into this detailed description, with eachclaim standing on its own as a separate embodiment of this invention.Having disclosed embodiments and the best mode, modifications andvariations may be made to the disclosed embodiments while remainingwithin the scope of the embodiments as defined by the following claims.

1-20. (canceled)
 21. A method of generating an immediate blockacknowledgement by a recipient station via partial state operation,comprising: receiving a data unit associated with a blockacknowledgement agreement between an originator station and therecipient station; generating and storing a temporary blockacknowledgement record if no temporary block acknowledgement record forthe agreement exists when the data unit is received; modifying thetemporary block acknowledgement record based on the received data unitif the temporary block acknowledgement record for the agreement existswhen the data unit is received; generating the immediate blockacknowledgement for the originator station based on the temporary blockacknowledgement record; and discarding the temporary blockacknowledgement record when a data unit is received from a differentoriginator station.
 22. The method of claim 21, wherein the temporaryblock acknowledgement record includes a bitmap.
 23. The method of claim21, wherein the data unit associated with the block acknowledgementagreement includes a media access control (MAC) protocol data unit(MPDU).
 24. The method of claim 21, further comprising: responding tothe originator station to establish the block acknowledgement agreement.25. The method of claim 21, further comprising: receiving a blockacknowledgement request from the originator station; and transmittingthe immediate block acknowledgement to the originator station inresponse to the block acknowledgement request.
 26. A method of managingan immediate block acknowledgement scoreboard by a recipient stationduring partial state operation, comprising: receiving a data unitassociated with a first block acknowledgement agreement between therecipient station and a first originator station; generating and storinga temporary block acknowledgement record if no temporary blockacknowledgement record for the first block acknowledgement agreementexists when the data unit is received; modifying the temporary blockacknowledgement record based on the received data unit if the temporaryblock acknowledgement record for the first block acknowledgementagreement exists when the data unit is received; receiving another dataunit associated with a second block acknowledgement agreement betweenthe recipient station and a second originator station that is differentfrom the first originator station; and discarding the temporary blockacknowledgement record after receiving the another data unit from thesecond originator station.
 27. The method of claim 26, wherein thetemporary block acknowledgement record includes a bitmap.
 28. The methodof claim 26, wherein the data unit associated with the first blockacknowledgement agreement includes a media access control (MAC) protocoldata unit (MPDU), and wherein the another data unit associated with thesecond block acknowledgement agreement includes another MPDU.
 29. Themethod of claim 26, further comprising: generating an immediate blockacknowledgement for the first originator station based on the temporaryblock acknowledgement record.
 30. The method of claim 26, furthercomprising: receiving a block acknowledgement request from the firstoriginator station; and transmitting an immediate block acknowledgementincluding the temporary block acknowledgement record to the firstoriginator station in response to the block acknowledgement request. 31.A method of managing an immediate block acknowledgement scoreboard by arecipient station during partial state operation, comprising: generatingand storing in a memory a temporary block acknowledgement record for ablock acknowledgement agreement between an originator station and therecipient station; maintaining the temporary block acknowledgementrecord as long as the recipient station receives data from theoriginator station; and discarding the temporary block acknowledgementrecord when the recipient station receives data from a different stationthan the originator station.
 32. The method of claim 31, wherein thetemporary block acknowledgement record includes a bitmap.
 33. The methodof claim 31, wherein the data from the originator station includes amedia access control (MAC) protocol data unit (MPDU), and wherein thedata from the different station includes another MPDU.
 34. The method ofclaim 31, further comprising: responding to the originator station toestablish the block acknowledgement agreement.
 35. The method of claim31, further comprising: receiving a block acknowledgement request fromthe originator station; and transmitting the immediate blockacknowledgement including the temporary block acknowledgement record tothe originator station in response to the block acknowledgement request.36. The method of claim 31, wherein the maintaining includes: modifyingthe temporary block acknowledgement record based on the received datafrom the originator station.